Ortho-formylated phenols and their derivatives are valuable intermediates in the preparation of products for the chemical, pharmaceutical and mining industries. Therefore, processes for making hydroxyarylaldehydes, and in particular, 2-hydroxyarylaIdehydes, have been well researched. It is well recognized that such hydroxyarylaldehydes can be made by reacting magnesium phenoxides with formaldehyde under anhydrous conditions.